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Need some eduction on twist rates....???

robert38-55robert38-55 Senior MemberPosts: 3,621 Senior Member
After reading and doing some research on twist rates I still don't get ???

...........Explain to me about twist rates between rifles, pistols,,, cannons, revolvers, machine guns, bar's and black powder guns, navel, guns, mortars, 105 howertizs, and gattlening guns rockets missiles, flintlocks, smooth bore guns etc... I don't have the knowledge and expertise gals and pals have here... Reading my gun magazine's, and online data I seemed to be confused???????????????
"It is what it is":usa:

Replies

  • BigslugBigslug Senior Member Posts: 8,251 Senior Member
    Longer bullets relative to bore diameter need to be spun faster - such as a 160 grain 6.5mm will need about one turn in 8", while the same weight in most modern .30 calibers will be happy at one turn in 12". Slower bullets need to be spun faster, which is why the .300 Blackout has a 1-7" twist for use with it's long, heavy, and slow 220 grain subsonic loads.
    WWJMBD?

    "Nothing is safe from stupid." - Zee
  • knitepoetknitepoet Senior Member Posts: 21,087 Senior Member
    The length and diameter of a bullet dictates how fast it has to be spinning to have gyroscopic stability. (Like Bigslug said, in a "wordier" fashion)

    Google "Greenhill formula" and it should explain it a LOT easier than I can type it out.

    Also, Robert A. Rinker's book "Understanding Firearms Ballistics" is a very good read, in an easy to understand format IMO.
    Seven Habits of Highly Effective Pirates, Rule #37: There is no “overkill”. There is only “open fire” and “I need to reload”.


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